Municipal waste is material discarded from residential, commerical, and some industrial establishments. The amount of waste generated in the year 2000 is expected to be in the range of 159 to 287 million tons per year, compared to estimates of current generation rates of 134 to 180 million tons. The most common method currently used to dispose of municipal waste is direct landfill. However, existing landfill capacity is being exhausted in many areas of the country and new landfills are becoming increasingly difficult to site. Because of these problems with direct landfill, increased emphasis will be made on reducing waste volume through combustion.
There are three basic types of facilities used to combust municipal waste. The predominant type is called "mass burn" because the municipal waste is combusted with a priority on consuming large amounts of material through-put. The combustors at mass burn facilities usually have overfeed stroker type grates. These combustors are field erected and individual combustors can range in size from 500 to 3,000 tons per day of municipal waste input. A second type of facility is the modular combustor. Modular combustors are typically shop-fabricated and range in size from 5 to 100 tons per day. A third method for combusting municipal waste is processing it to produce refuse derived fuel (RDF), then combusting the RDF in a waterwall boiler. RDF offers the advantage of producing a more homogeneous fuel and increasing the percentage of municipal waste which is recycled.
Almost all existing facilities have some type of particulate matter emission controls. Many existing modular combustors attempt to control particulate matter using a two-stage combustion process, most of these facilities also have add-on controls. Other facilities use add-on controls, such as ESPs, dry scrubbers, wet scrubbers, and baghouses. Almost all new facilities will have add-on particulate controls such as ESPs and baghouses. In addition, a significant number may include acid gas controls. However, total emissions from MWC are still expected to increase due to the large increase in the total capacity of the population.
Those concerned with these and other problems recognize the need for an improved municipal waste incinerator.